1. Field
Embodiments of the present invention generally relate to the field of high-resolution imagery. More specifically, the present invention refers to the generation of high-resolution images in a variable depth of field environment.
2. Background
Many satellite sensors provide high-resolution panchromatic (black and white) imagery along with lower resolution multi-spectral (color) imagery. Image fusion techniques, such as pan sharpening, are used to combine these multiple images into a composite product. More specifically, pan sharpening methods process the multi-spectral image with the coarse spatial resolution into a fine spatial color image by fusing the multi-spectral image with the high-resolution panchromatic image. As a result, the high-resolution color image preserves the original color fidelity and allows for better visualization and interpretation. FIG. 1 illustrates a conventional pan sharpening device 100, where a multi-spectral image sensor 110 is coupled to a panchromatic image sensor 120.
Satellite imagery typically captures images that have a narrow depth of field. Depth of field refers to the range in front of and beyond an object that appears to be in focus. In imagery applications with a narrow depth of field, pan sharpening techniques provide a reliable method to generate high-resolution color images. However, for images with a wide depth of field, the resolution of color images generated from pan sharpening techniques may be degraded. It is desirable to implement techniques to account for a wide depth of field, such that high-resolution images may be generated using pan sharpening methods.
Additionally, resolution may be degraded when near-field images are captured using pan sharpening techniques due to parallax. Parallax refers to a perceived shift of an imaged object against a background caused by the distance between apertures of the panchromatic and multi-spectral image sensors. Existing satellite and other airborne sensors do not have to account for parallax since the focal length between the sensors and the object being imaged (e.g., the ground) is large enough such that the distance between apertures of the panchromatic and multi-spectral image sensors is negligible. When the focal length is decreased, such as in near-field imaging, loss of resolution due to parallax becomes a greater issue.